[PATCH bpf 0/2] Revert "xsk: support redirect to any socket bound to the same umem"

[Magnus Karlsson <magnus.karlsson@gmail.com>]

Revert "xsk: support redirect to any socket bound to the same umem"

This patch introduced a potential kernel crash when multiple napi
instances redirect to the same AF_XDP socket. By removing the
queue_index check, it is possible for multiple napi instances to
access the Rx ring at the same time, which will result in a corrupted
ring state which can lead to a crash when flushing the rings in
__xsk_flush(). This can happen when the linked list of sockets to
flush gets corrupted by concurrent accesses. A quick and small fix is
unfortunately not possible, so let us revert this for now.

[  306.997548] BUG: kernel NULL pointer dereference, address: 0000000000000008
[  307.088372] #PF: supervisor read access in kernel mode
[  307.149079] #PF: error_code(0x0000) - not-present page
[  307.209774] PGD 10f131067 P4D 10f131067 PUD 102642067 PMD 0
[  307.276608] Oops: 0000 [#1] SMP
[  307.313712] CPU: 3 PID: 1919 Comm: sp1 Tainted: P           OE     5.15.117-1-ULP-NG #1
[  307.408219] Hardware name: Radware Radware/Default string, BIOS 5.25 (785A.015) 05/11/2023
[  307.505779] RIP: 0010:xsk_flush+0xb/0x40
[  307.552099] Code: a0 03 00 00 01 b8 e4 ff ff ff eb dc 49 83 85 a0 03 00 00 01 b8 e4 ff ff ff eb cd 0f 1f 40 00 48 8b 87 40 03 00 00 55 48 89 e5 <8b> 50 08 48 8b 40 10 89 10 48 8b 87 68 03 00 00 48 8b 80 80 00 00
[  307.773694] RSP: 0000:ffffb7ae01037c80 EFLAGS: 00010287
[  307.835401] RAX: 0000000000000000 RBX: ffffa0a88f8ab768 RCX: ffffa0a88f8abac0
[  307.919670] RDX: ffffa0a88f8abac0 RSI: 0000000000000004 RDI: ffffa0a88f8ab768
[  308.003922] RBP: ffffb7ae01037c80 R08: ffffa0a10b3e0000 R09: 000000000000769f
[  308.088172] R10: ffffa0a1035ca000 R11: 000000000d7f9180 R12: ffffa0a88f8ab768
[  308.172405] R13: ffffa0a88f8ebac0 R14: ffffa0a2ef135300 R15: 0000000000000155
[  308.256635] FS:  00007ffff7e97a80(0000) GS:ffffa0a88f8c0000(0000) knlGS:0000000000000000
[  308.352186] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[  308.420043] CR2: 0000000000000008 CR3: 000000010cf6e000 CR4: 0000000000750ee0
[  308.504309] PKRU: 55555554
[  308.536296] Call Trace:
[  308.565209]  <TASK>
[  308.590026]  ? show_regs+0x56/0x60
[  308.630218]  ? __die_body+0x1a/0x60
[  308.671433]  ? __die+0x25/0x30
[  308.707529]  ? page_fault_oops+0xc0/0x440
[  308.754897]  ? do_sys_poll+0x47c/0x5e0
[  308.799188]  ? do_user_addr_fault+0x319/0x6e0
[  308.850659]  ? exc_page_fault+0x6c/0x130
[  308.896992]  ? asm_exc_page_fault+0x27/0x30
[  308.946398]  ? xsk_flush+0xb/0x40
[  308.985546]  __xsk_map_flush+0x3a/0x80
[  309.029824]  xdp_do_flush+0x13/0x20
[  309.071043]  i40e_finalize_xdp_rx+0x44/0x50 [i40e]
[  309.127653]  i40e_clean_rx_irq_zc+0x132/0x500 [i40e]
[  309.202736]  i40e_napi_poll+0x119/0x1270 [i40e]
[  309.256285]  ? xsk_sendmsg+0xf4/0x100
[  309.315969]  ? sock_sendmsg+0x2e/0x40
[  309.359244]  __napi_poll+0x23/0x160
[  309.400482]  net_rx_action+0x232/0x290
[  309.444778]  __do_softirq+0xd0/0x270
[  309.487012]  irq_exit_rcu+0x74/0xa0
[  309.528241]  common_interrupt+0x83/0xa0
[  309.573577]  asm_common_interrupt+0x27/0x40

Thanks: Magnus

Magnus Karlsson (2):
  Revert "xsk: support redirect to any socket bound to the same umem"
  Revert "xsk: document ability to redirect to any socket bound to the
    same umem"

 Documentation/networking/af_xdp.rst | 33 ++++++++++++-----------------
 net/xdp/xsk.c                       |  5 +----
 2 files changed, 15 insertions(+), 23 deletions(-)


base-commit: 2317dc2c22cc353b699c7d1db47b2fe91f54055c
--
2.45.1